This invention relates generally to auto-focus control for optics. More specifically, the present invention relates to an auto-focus control device having a configurable focus area.
Automatic-focusing cameras are well known in the art. In a conventional camera, a viewfinder displays a field of view and a portion of that field is a focus area. The camera comprises circuitry adapted to maximize the resolution of the image within the focus area. Although widely used and usually effective, conventional auto-focusing does have its shortcomings.
One particular drawback is the tendency for the focus area to be fixed within the field of view. Typically, the focus area is located toward the center of the field of view and cannot be moved. Although such a configuration is suitable in most situations where the object of the photograph is placed in the center of the field of view, occasionally the preferred composition of the photograph places the object elsewhere in the field of view. In such a case, the object tends to be blurred because the automatic focusing is performed only in the above-mentioned focus area regardless of the position of the intended object.
To solve this problem, cameras have been developed with xe2x80x9cfocus lockxe2x80x9d to facilitate focusing on objects other than those located in the center of the field of view. More specifically, focus lock enables a photographer to focus on an off-center object by first placing the focus area over the object (that is, centering the object), allowing the lens to focus, locking the focus, and then, with the focus locked, changing the composition of a picture (for example, positioning the object off to a side) before taking the photograph. Unfortunately, xe2x80x9cphoto-opportunitiesxe2x80x9d can be missed with these cameras since the focus must be locked before composing the shot.
Other cameras have been developed with sophisticated logic and control for measuring the distance to a plurality of objects within the field of view, determining the nearest object of the plurality, and focusing on that object. The object to be brought into focus, however, is not always the nearest. Thus, the resulting photograph may be focused on the wrong object rendering the intended object blurry.
Recently, cameras have been developed having a multiplicity of focus areas which can be selected by the user. Although affording the user with greater flexibility in composing his or her photograph, these cameras are nevertheless limited to predetermined focus areas having fixed positions and sizes.
Therefore, the applicant has identified the need for a camera having a configurable focus area that is not constrained by preset conditions. The present invention fulfills this need among others.
The present invention overcomes the aforementioned problems with convention auto-focus cameras by providing for a configurable focus area. A configurable focus area enables the user to position the desired focus area anywhere within the field of view. This way, the user is not limited to predefined focus areas that may not target the object upon which the user desires to focus. Additionally, the configurable focus area of the present invention may be adapted to allow the user to adjust the size and/or shape of the area.
One aspect of the present invention is an imaging device having a focus area configuration device and supporting circuitry for configuring a focus area within the field of view. In a preferred embodiment, the device comprises: (a) an imaging system for generating a video signal of an image within a field of view, wherein the imaging system is adapted to adjust the focal point of the image according to an adjustment signal; and (b) a focusing system comprising: (i) a configuration device for positioning a focus area within the field of view; and (ii) autofocusing circuitry coupled to the imaging system and the configuration device, the autofocusing circuitry being configured for correlating a configured focus area to a portion of the video signal, analyzing the portion for resolution, and effecting an adjustment signal to adjust the focal point of the image to improve the resolution of the configured focus area. Preferably, the autofocusing circuitry comprises a digital processor.
Another aspect of the present invention is the provision of the above-mentioned focusing system for use in an imaging device.
Yet another aspect of the present invention is the provision of the above-mentioned data processor for use in a camera""s focusing system.
Still another aspect of the present invention is the provision of a method of using the above-mentioned imaging device: In a preferred embodiment, the method comprises the steps of: (a) moving the imaging device relative to an object to obtain a desired field of view; (b) manipulating the above-mentioned configuration device to position the focus area over the object within the field of view; (c) using the focusing system to improve the resolution of the focus area; and (d) activating a video signal processing system to transfer the video signal to a storage medium.